Sensor configuration for caustic environments

ABSTRACT

Methods and apparatuses for using a sensor. A sensor is selectively coupled with an environmental condition for which the sensor is designed when a first predetermined event occurs. The sensor is selectively decoupled from the environmental condition when a second predetermined event occurs.

TECHNICAL FIELD

[0001] This invention relates generally to the environment surrounding a sensor, and more particularly to sensors that operate in detrimental environmental conditions.

BACKGROUND

[0002] As technology continues its rapid growth and increase in sophistication, it is increasingly desirable to include additional sensors for devices, to provide feedback on a variety of conditions. In many cases, the sensors may be quite expensive. Further complicating things, the environmental condition that the sensor detects may often be detrimental to the lifespan of the sensor.

[0003] For example, NO_(x) sensors may be used to measure the NO_(x) in the exhaust of engines. However, the exhaust flow from an engine may be caustic to many NO_(x) sensor designs. In some instances the lifespan of a NO_(x) sensor may be approximately 2000 hours of operation, whereas the desired lifespan is at least 8000 hours, and 20,000 would be preferred. This, combined with the current price tag up to $2,000 for a typical NO_(x) sensor creates an untenable economic situation for engine manufacturers and end users.

SUMMARY OF THE INVENTION

[0004] The present invention provides methods and apparatuses for using a sensor. A sensor is selectively coupled with an environmental condition for which the sensor is designed when a first predetermined event occurs. The sensor is selectively decoupled from the environmental condition when a second predetermined event occurs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 shows an apparatus according to one embodiment of the invention.

DETAILED DESCRIPTION

[0006]FIG. 1 shows an apparatus 10 according to one embodiment of the invention. The apparatus 10 includes an exhaust path 12, such as an exhaust manifold, from a combustion chamber of an engine (not shown).

[0007] A control valve 14 is coupled with the exhaust path 12. The control valve 14 may receive a control signal (“CONTROL”) by any of a variety of ways known to those skilled in the art. The control valve 14 selectively couples the exhaust flow in the exhaust path 12 with either a first exhaust flow path 16 or a second exhaust flow path 18 as a function of the control signal CONTROL.

[0008] The control signal may take various forms. For example, it may be an electrical signal, either digital or analog, or it may be a mechanical signal, such as movement of a linkage. It may also be other forms known to those skilled in the art. The control signal CONTROL may be transmitted based on whatever design characteristics are desired, such as when a first event occurs, including the passage of a predetermined amount of time.

[0009] The control valve 14 may isolate the second exhaust flow path from the exhaust path 12 and the first exhaust flow path 14 completely, or only partially. The control valve 14 may be any of a variety of devices known to those skilled in the art that are suitable to perform the functions described herein.

[0010] A sensor 20, such as a NO_(x) sensor or any of a variety of other sensing devices, may be coupled with the second exhaust flow path 18 by ways known to those skilled in the art.

[0011] In another embodiment of the invention, an actuator (not shown) may physically move the sensor 20 into and out of the first exhaust flow path 16. In these embodiments, the second exhaust flow path 18 may be omitted. Alternately, an actuator may selectively isolate, e.g., cover and uncover, the sensor 20, thereby exposing it to the exhaust flow of the engine.

[0012] A flush valve (not shown) may be coupled with the second exhaust flow path 18. The flush valve may transmit a first fluid, such as air or other liquid, gas, or mixture thereof to flush the environmental condition from around the sensor 20. Depending on the desired configuration, the flush valve may be integrated into the control valve 20.

INDUSTRIAL APPLICABILITY

[0013] The apparatus 10 or other embodiments of the invention may be used to selectively couple a sensor with an environmental condition for which the sensor is designed when a first predetermined event occurs. One such example of a predetermined event is the passage of a predetermined amount of time. Other predetermined events known to those skilled in the art could also be used. When a measurement of the environmental condition is not desired or needed (e.g. when a second predetermined event occurs), the sensor 20 may be decoupled from the environmental condition. The environmental condition may be any of a variety of physical conditions known to those skilled in the art.

[0014] For example, in embodiments of the invention where the sensor 20 is a NO_(x) sensor, the exhaust flow from the engine may periodically be directed by the control valve 14 to the second exhaust flow path 18, and thereby to the sensor 20. The sensor 20 makes its measurement of the NO_(x) in the exhaust, and transmits this measurement. The control valve 14 then redirects the exhaust from the engine into the first exhaust path 16. Thus, the NO_(x) sensor is not subject to the full exhaust from the engine except when a measurement is taken.

[0015] The optional flush valve may be used to cleanse the sensor 20 so that the environmental condition does not degrade the sensor 20 when the sensor 20 is not needed to measure the environmental condition.

[0016] From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 

1. A method for using a sensor, comprising: selectively coupling a NOx sensor with a diesel engine exhaust flow when a first predetermined event occurs; and selectively decoupling the sensor from the flow when a second predetermined event occurs.
 2. The method of claim 1 wherein selectively coupling comprises at least one of: directing the flow in proximity to the sensor so that the sensor is operable to monitor NOx in the flow; and directing the sensor into proximity with the flow so that the sensor is operable to monitor NOx in the flow.
 3. The method of claim 1 wherein the first predetermined event comprises a passage of a first predetermined amount of time.
 4. The method of claim 1 wherein the second predetermined event comprises a passage of a second predetermined amount of time.
 5. The method of claim 1 further comprising: cleansing the area in the proximity of the sensor when the sensor is decoupled from the flow.
 6. An apparatus for sensing a condition, comprising: a first exhaust flow path operable to transmit an exhaust flow from a diesel engine; a second exhaust flow path operable to transmit an exhaust flow from the engine; a control valve coupled with the first exhaust flow path and the second exhaust flow path, the control valve operable to receive an exhaust flow from the engine and to selectively transmit the exhaust flow from the engine to one of the first and second exhaust flow paths as a function of a control signal; a NOx sensor coupled with the second exhaust flow path, the sensor operable to monitor the NOx in the exhaust flow in the second exhaust flow path and to transmit a first signal as a function thereof.
 7. The apparatus of claim 6 wherein the control valve is further operable to isolate the second exhaust flow path from the exhaust flow of the engine as a function of the control signal.
 8. The apparatus of claim 6 further comprising a flush valve coupled with the second exhaust flow path, the flush valve operable to transmit a first fluid to the second exhaust flow path as a function of a second control signal.
 9. The apparatus of claim 8 wherein the first fluid comprises air.
 10. The apparatus of claim 8 wherein the flush valve is integrated with the control valve.
 11. A apparatus for sensing a condition, comprising: a first exhaust flow path operable to transmit an exhaust flow from a diesel engine; a NOx sensor operable to monitor the NOx in the exhaust flow in proximity to the sensor and to transmit a first signal as a function thereof; and a first actuator operable to selectively couple and isolate the sensor from the first exhaust flow path as a function of a control signal.
 12. The apparatus of claim 11 wherein the first actuator is operable to insert the first sensor into the first exhaust flow path as a function of the control signal. 